Tubing hanger with coupling assembly

ABSTRACT

A tubing hanger ( 1 ) landing in a tubular element ( 101 ), having a coupling assembly ( 11 ) for hydraulic coupling between the tubing hanger ( 1 ) and the element. A coupling element ( 17 ) moves radially between an outer coupled position and an inner non-coupled position. An actuation element ( 25 ) with a contact surface ( 25   f ) exerts an outward actuation force onto an inner actuation surface ( 17   a ) of the coupling element. The actuation element comprises two actuation sections ( 25   x   , 25   y ) exposed to a outward force from an actuation arrangement ( 27 ). The contact surface ( 25   f ) has a distance the actuation sections. The actuation element moves in the radial outward direction so that the movement of at least one of the two actuation sections ( 25   x   , 25   y ) stops after the radial movement of the contact surface ( 25   f ) stops. The contact surface ( 25   f ) movement halts as the coupling element ( 17 ) reaches the coupled position.

The present invention relates to a tubing hanger with a couplingassembly which is adapted to establish hydraulic coupling with anoppositely arranged counterpart on an inner face of a tubular element,such as a Xmas tree.

BACKGROUND

In the oil industry and particularly in the subsea field, it is commonto provide arrangements that can connect and disconnect electricconnections and fluid connections remotely. For instance, hydraulicconnections and channels are used to control pressures and to providemechanical movement of equipment, such as locking and unlocking oflatches and valves. Furthermore, electrical connections andcommunication paths are provided for measurement of e.g. temperaturesand pressures.

An example of such remotely (diverless or even ROV-less) establishedconnections is the connections between a tubing hanger which is landedin the spool of a Christmas tree (XT) and the XT itself. Patentpublication U.S. Pat. No. 6,158,716 describes a tubing hanger (TH)having a plurality of radially actuated coupling elements. On theradially outwardly facing side, the coupling elements have an interfaceadapted for engagement (i.e. abutment) with a facing counterpartarranged in the XT spool. As the TH is landed in the XT spool, thecoupling elements are moved radially into engagement with thecounterpart to establish sealed hydraulic couplings. The ends ofhydraulic channels of the coupling elements and facing counterparts arealigned and a surrounding sealing is established encircling the saidfacing channel ends. The appurtenant FIG. 3 is from U.S. Pat. No.6,158,716, and shows the coupling element (20) arranged in the tubinghanger.

The sealing of the solution described in the patent publication U.S.Pat. No. 6,158,716 is established by forcing a seal carrying part (thecoupling element 20) against a sealing surface (cf. sealing surface 203of the prior art FIG. 3) of the facing part. Due to the substantialpressures which may be present in equipment associated with subseawells, the two facing parts are forced against each other with aconsiderable force to ensure proper sealing. This force needs to beabove a lower threshold in order to ensure the sealing function, as wellas to be below an upper threshold in order to maintain the mechanicalintegrity of the associated parts. Hence one needs a solution whichprovides a pre tension between a selected upper and lower force limit.

Another goal when forcing the coupling element radially into sealingengagement with the counterpart, is to force it in a strict radialdirection with the resultant force in the axial centre of the couplingelement. That is, one needs to ensure that the sealing surface is forcedagainst the facing counterpart with an even pressure throughout the areaof the sealing surface.

THE INVENTION

According to a first aspect of the invention, there is provided a tubinghanger adapted to land in a tubular element, such as a Xmas tree, andcomprising a coupling assembly which is adapted for establishment of ahydraulic coupling between the tubing hanger and the tubular element.According to the invention, the coupling assembly comprises a couplingelement adapted to move radially between an outer coupled position andan inner non-coupled position. The term radially is with respect to anaxially running centre axis of the tubular element and/or the tubinghanger itself. The coupling element exhibits an outer surface adapted toestablish said hydraulic coupling with an opposite and inwardly facingsurface of the tubular element when forced against it. The said inwardlyfacing surface of the tubular element may very well be the surface of acomponent attached to the tubular element, such as a penetrator arrangedin a wall of the tubular element. The coupling element comprises ahydraulic channel adapted to align with a hydraulic channel in thetubular element. The coupling element comprises a radially inneractuation surface.

Furthermore, according to the present invention, the coupling assemblyalso comprises an actuation element having a contact surface which isadapted to exert an actuation force onto the inner actuation surface ina radially outward direction. The actuation element exhibits anelongated shape and comprises two actuation sections which are adaptedto be exposed to a radially outward directed force from an actuationarrangement. The contact surface is arranged with a distance from bothof said actuation sections. The actuation element is adapted to be movedin the radial outward direction in such way that the movement of atleast one of the two actuation sections will stop after the radialmovement of the contact surface has stopped. The movement of the contactsurface is halted when the coupling element reaches the coupledposition.

The actuation element will thus function as a leaf spring, maintaining aradial outward directed force onto the coupling element. As will beappreciated by the person skilled in the art, the preload will bedetermined by the spring stiffness.

The distance between the contact surface and the two actuation sectionsis preferably a distance along the axial direction. However, thedistance could also be in a tangential direction.

With the term elongated shape of the actuation element is to beunderstood a shape of its cross section which is sufficiently thin withrespect to its extension in the radial and/or tangential direction,which makes the actuation element flexible. The flexibility of theactuation element has the function of making the movement of one of thesaid actuation sections possible when the movement of the contactsurface has been halted. This additional movement will result in apreloading of the coupling element in the radial outward direction, i.e.towards the facing tubular element. Thus the actuation element coulde.g. be a flexible bar-shaped component or a flexible plate-shapedcomponent.

In one embodiment, the actuation element comprises two parallel inclinedsurfaces which are adapted to slide simultaneously along two facinginclined surfaces of the actuation arrangement. In this way theactuation element does not alter its orientation. It will only alter itsposition, as it is moved radially outwards by engagement with theactuation arrangement. Strictly speaking, the two actuation sections ofthe actuation element will however move a bit further than its contactsurface, due to the preload function as discussed above.

The contact surface of the actuation element or the inner surface of thecoupling element may exhibit a spherical or convex, curved shape.Preferably the coupling element exhibits such a surface. As will bedescribed in the example of embodiment further below, this featuresensures a central positioning of the forces between the actuationelement and the coupling element. This will further ensure an even forcedistribution between the coupling element and the facing surface of thetubular element.

In the coupled position two supporting surfaces of the actuationarrangement can be adapted to abut against oppositely arranged andparallel extending actuation surfaces of the actuation element. Of thesaid parallel extending actuation surfaces one is arranged on eachactuation section. In this embodiment, the supporting surfaces of theactuation arrangement and the actuation surfaces of the actuationelement are preferably in parallel with an axially extending centre axisof the tubing hanger. In this way there will not arise axially directedforces between the actuation arrangement and the actuation element.

According to an embodiment the coupling assembly is designed in suchmanner that during a first actuation of the coupling assembly, theactuation element is adapted to deform both in an elastic and plasticmanner when the at least one of the two actuation sections moves adistance after the movement of the contact surface stops. This featuremakes the actuation element adapt to the other parts of the couplingassembly and the tubular element when being used the first time.

Although the tubing hanger according to the invention is particularlyadvantageous in connection with subsea wells, it may also be employed inassociation with onshore wells, as will be appreciated by the personskilled in the art.

EXAMPLE OF EMBODIMENT

While the main features of the present invention have been describedabove, a more detailed example of embodiment will now be described withreference to the drawings, in which

FIG. 1 shows the lower part of a tubing hanger, which is provided withthe coupling assembly according to the invention in a non-coupledposition;

FIG. 2 shows the parts of FIG. 1, however with the coupling assembly inthe coupled position;

FIG. 3 is a perspective view of a coupling assembly according to theprior art;

FIG. 4 is an enlarged cross section view of parts of the couplingassembly according to the invention, in a non-coupled state;

FIG. 5 is a more detailed cross section view of the coupling assemblyshown in

FIG. 4, in the non-coupled state;

FIG. 6 is the same cross section view as FIG. 5, however with thecoupling assembly in an intermediate state;

FIG. 7 is the same cross section view as FIG. 5 and FIG. 6, however withthe coupling assembly in a coupled state;

FIG. 8 is a stand-alone cross section view of a movable actuationportion of the main body;

FIG. 9 is a stand-alone cross section view of an actuation element ofthe coupling assembly;

FIG. 10 is an enlarged cross section view of a coupling element of thecoupling assembly;

FIG. 11 is a side view of the inner face of a carrier ring of thecoupling assembly;

FIG. 12 is a perspective cutaway view of parts of the coupling assembly;

FIG. 13 is a cross section side view of parts of the coupling assemblyin a coupled state; and

FIG. 14 is the same view as FIG. 13 in a non-coupled state.

FIG. 1 shows a tubing hanger (TH) 1 (actually it is a lower part or apenetrator assembly of a tubing hanger, it is however referred to as atubing hanger herein for simplicity) provided with a coupling assembly11 according to the present invention. The coupling assembly 11 has acarrier ring 13 that extends about the circumference of the TH 1. Thecarrier ring 13 has a plurality of holes 15 that extend through thecarrier ring 13 in a radial direction. Within the holes 15 of thecarrier ring 13 there are arranged coupling elements 17. The couplingelements 17 are adapted to slide back and forth in a radial directionwithin the holes 15 of the carrier ring 13. Through the carrier ring 13extends a main body 19. At the upper end of the main body 19 isconnected to additional parts (not shown) of the TH. The carrier ring 13is reciprocally suspended on the main body 19, in such way that thecarrier ring 13 and the main body 19 can move with respect to each otherin the axial direction. This movement takes place during coupling anddecoupling of the coupling assembly 11.

At the lower section of the tubing hanger 1 shown in FIG. 1 there is anorientation sleeve 118.

When the TH 1 is arranged within a tubular element, such as the spool ofa XT (not shown in FIG. 1 and FIG. 2), the coupling elements 17 will beforced in a radial outward direction and into sealing contact with afacing counterpart (cf. FIG. 4 to FIG. 6). When the TH 1 shall beretrieved, the coupling elements 17 will be moved back, in a radialinwards direction, in order to prevent them from touching any part ofthe tubular element (e.g. the XT spool) when the TH 1 is retrieved. FIG.1 shows the coupling assembly 11 in a non-coupled state, i.e. with thecoupling elements 17 in a retracted position. The process of moving thecoupling elements 17 in said radial direction will be explained furtherbelow.

FIG. 2 shows the same parts as FIG. 1, however with the couplingassembly in the coupled position, i.e. in the radially extendedposition. In the coupled position the main body 19 is in a lowerposition with respect to the carrier ring 13 than in the non-coupledposition shown in FIG. 1.

Also shown in FIG. 1 and FIG. 2 are a plurality of hydraulic lines(pipes) 21 which extend from the lower part of the TH 1 to the couplingelements 17. A part of the hydraulic lines 21 are arranged in slits 23in the orientation sleeve 118. The hydraulic lines 21 are sufficientlyflexible to allow for the radial movement of the coupling elements 17during coupling and decoupling.

FIG. 3 is a perspective view of a prior art solution (FIG. 12 of U.S.Pat. No. 6,158,716). As with the coupling assembly 11 according to thepresent invention, the prior art solution has a carrier ring (30) withholes. In each of the holes there is a coupling element (20) adapted tobe forced out in a radial direction in order to make a sealing couplingwith a facing counterpart. Furthermore, as with the coupling assembly 11according to the present invention, the prior art solution shown in

FIG. 3 is adapted to maintain a pre-load on the coupling element in theradial direction, when the coupling element is in the coupled position.In the prior art solution, however, the pre-load is based on friction,whereas another technique is used in the coupling assembly 11 accordingto the present invention. For an explanation of the prior art pre-loadsolution it is referred to the publication. The solution according tothe present invention will be described in the following.

The process of moving and preloading the coupling elements 17 into thecoupled position will now be described with reference to FIG. 4 to FIG.7. FIG. 4 shows a cross section side view of parts of the couplingassembly 11 (left) which has landed inside the spool 101 of a XT (right)of a subsea well. Also shown is a section of an upper part 1 a of thetubing hanger 1. In the spool 101 is a through hole 103 in which thereis arranged a penetrator 105 with a hydraulic channel 107. At theradially inner side of the penetrator 105 (left hand side in FIG. 4) thepenetrator 105 exhibits a channel mouth 109 surrounded by a sealingsurface 111. The object of the coupling assembly 11 in the TH 1 is tomove and preload the coupling element 17 radially outwards from theretracted non-coupled position shown in FIG. 4 to the extended coupledposition in which the coupling element 17 abuts and seals against thesealing surface 111 of the penetrator 105.

Down from the coupling element 17 extends the hydraulic line 21. Thehydraulic line 21 communicates with a hydraulic channel 21 a within thecoupling element 17. When the TH 1 has landed, a coupling element mouth21 b is aligned with and faces the channel mouth 109 of the penetrator105. Thus, when the coupling element 17 is moved radially outwards(towards the right in FIG. 4) a hydraulic communication will beestablished between the hydraulic line 21 and the hydraulic channel 107in the penetrator 105.

Radially within the coupling element 17 is arranged an actuation element25 and radially within the actuation element 25 is an actuationarrangement in the form of an axially movable actuation portion 27. Inthis embodiment the axially moving actuation portion 27 is a part of themain body 19. Also shown in FIG. 4 (as well as in FIG. 1) is one of aplurality of spiral springs 29, the purpose of which will be explainedfurther below.

FIG. 5, FIG. 6, and FIG. 7 show enlarged views of parts the couplingassembly 11 in a non-coupled state, an intermediate state, and in acoupled state, respectively. Referring first to FIG. 5, when the TH 1 islanded in the spool 101 of the XT, a carrier ring landing surface 13 awill engage a spool landing shoulder 101 a. This prevents the carrierring 13 to move further downwards within the spool 101. The main body 19of the TH 1 will however continue to move further down within the spool101. This further movement will make the axially movable actuationportion 27 slide downwards along the inner surface of the actuationelement 25. The actuation element 25 is fixed in the axial direction,but can be moved in the radial direction to force and move the couplingelement 17 radially outwards. In FIG. 4 and FIG. 5 the axially movableactuation portion 27 has not yet moved with respect to the actuationelement 25, which thus is in the radially inner position. Thus thecoupling element 17 is not in the coupled position. The coupling element17 has an outer surface 17 b adapted to abut against the sealing surface111 of the penetrator 105. As appears from FIG. 5, the outer surface 17b has not yet come into contact with the sealing surface 111.

In the intermediate state shown in FIG. 6, however, the axially movableactuation portion 27 has been moved a distance downwards with respect tothe carrier ring 13 and the actuation element 25. During this movement afirst and second inclined surface 25 c, 25 d of the actuation element 25are slid along facing and substantially parallel inclined surfaces 27 c,27 d of the axially movable actuation portion 27. The radially outwardlydirected movement of the actuation element 25 has moved the couplingelement 17 into abutment with the facing sealing surface 111 of thepenetrator 105. One should note that there is substantially no mutualmovement between the coupling element 17 and the actuation element 25,as they until this point have moved together in the radial direction.The actuation element 25 exhibits a contact surface 25 f which abuts andtransmits the radially directed force onto the coupling element 17.

Still referring to the intermediate state shown in FIG. 6, although thecoupling element 17 has been moved into abutment with the sealingsurface 111 of the penetrator 105, the first and second actuationsurfaces 25 c, 25 d of the actuation element 25 have still not slid allthe way until to the end of the first and second inclined surfaces 27 c,27 d. Thus, as the axially movable actuation portion 27 continues tomove downwards, the upper and lower part of the actuation element 25 areforced an additional distance radially outwards.

Referring to the coupled state shown in FIG. 7, when the first andsecond inclined surfaces 25 c, 25 d of the actuation element 25 haveslid beyond the facing first and second inclined surfaces 27 c, 27 d ofthe axially movable actuation portion 27, a first actuation surface 25 aof the actuation element 25 enters into contact with a facing firstsupporting surface 27 a of the axially movable actuation portion 27.Correspondingly, a second actuation surface 25 b enters into contactwith a second supporting surface 27 b of the actuation portion 27. Onthe actuation element 25, the first actuation surface 25 a is arrangedin an upper first actuation section 25 x of the actuation element 25,whereas the second actuation surface 25 b is arranged at a lower secondactuation section 25 y. The first and second inclined surfaces 25 c, 25d of the actuation element 25, are also arranged in the first and secondactuation sections 25 x, 25 y, respectively. The contact surface 25 fabutting the coupling element 17 (i.e. abutting the coupling elementinner surface 17 a, cf. FIG. 10), is arranged at a mid section of theactuation element 25 and has a distance to both the first and secondactuation sections 25 x, 25 y.

The person skilled in the art will now appreciate, by referring to FIG.4 to FIG. 7, that the first and second actuation surfaces 25 a, 25 b ofthe actuation element 25 have been moved a further radial distance thanthe contact surface 25 f has. This results in a pre-tensioning of thecoupling element 17 in the radial outward direction. In the coupledstate the actuation element 25 will thus function as a preloaded leafspring.

For the sake of clarity, FIG. 8 and FIG. 9 show stand-alone crosssection views of the axially movable actuation portion 27 and theactuation element 25, making the positions of the various surfaces morevisible. At the mid section of the axially movable actuation portion 27there is an outward facing passive surface 27 e. Correspondingly, at themid section of the actuation element 25 there is an inward facingpassive surface 25 e. One should note that during actuation of thecoupling element 17, i.e. during movement of the actuation element 25from the non-coupled state of FIG. 5 to the coupled state of FIG. 7, theactuation element 25 substantially does not alter its orientation, onlyits position. That is, it does not pivot. As mentioned above, however,its shape will be slightly altered during the preload function, howeveronly in an elastic manner.

One could also imagine an actuation element (in the form of a leafspring) that is able to deform plastically during the first assembly. Insuch a case the plastic deformation could account for and adopt to theindividual tolerances of each unique tubing hanger. One would then haveto ensure that the actuation element has the ability to have asufficient remaining elastic range after being plastically deformed.

FIG. 10 shows a principle sketch of the coupling element 17 in contactwith the contact surface 25 f of the actuation element 25. The couplingelement 17 is on its radially inner surface provided with an inneractuation surface in the form of a coupling element inner surface 17 awhich abuts the contact surface 25 f. The coupling element inner surface17 a has a spherical surface or a curved surface adapted to contact thecontact surface 25 f of the actuation element 25 substantially at thecentre part of the coupling element inner surface 17 a. This featureensures that the force from the actuation element 25 onto the couplingelement 17 remains substantially at the centre portion of the couplingelement inner surface 17 a, even if there should be a small change ofangle between the two parts. Moreover, this feature ensures that theresultant force from the coupling element 17 onto the sealing surface111 of the penetrator 105 also will be located substantially at thecentral portion. This provides an even force distribution on the sealingsurfaces (or seals) adapted for sealing the coupling between thecoupling element 17 and the penetrator 105.

Instead of having the coupling element inner surface 17 a sphericallyshaped or curved, one could have the contact surface 25 f of theactuation element curved or spherical. However, one would then have toensure that the apex of the contact surface 25 f will indeed contact thecoupling element 17 at its center portion.

Encircling the coupling element mouth 21 b there may be arranged sealsadapted for sealing against the sealing surface 111 of the penetrator105.

FIG. 11 shows some parts of the coupling assembly 11, seen from theradial inside of the carrier ring 13. At the right hand side of FIG. 11,one can see how the coupling element 17 is arranged in a hole 15 of thecarrier ring 13 and capable of moving a distance in the radialdirection. The hydraulic channel 21 a in the coupling element 17 is alsoindicated, and has connection to the hydraulic line 21. Radially withinthe coupling element 17 the actuation element 25 is shown. In additionto the three shown coupling elements 17, an electrical coupler 117 isalso shown. This coupler is however not engaged by an actuation elementof the kind actuating the other coupling elements 17. For illustrationalpurpose one of the actuation elements 25 is removed in this drawing.

Further to the left in FIG. 11 there are shown two additional actuationelements 25. In this view one can see that they are provided with twoprotruding pins 31 at their upper end. The protruding pins 31 eachextends into a retaining groove 33 which ensures that the actuationelement 25 will not move in the axial direction, but allows it to movein the radial direction. The retaining groove 33 is constituted by aportion of the carrier ring 13 and a retaining element 35 which is fixedto the carrier ring 13 with a bolt. A retracting member 37 is attachedto the main body 19. The retracting member 37 is arranged for pullingthe coupling element 17 and the actuation element 25 radially inwardsduring retrieval of the tubing hanger 1. This will be discussed belowunder reference to FIG. 13 and FIG. 14.

FIG. 12 is an enlarged perspective cross section view of parts of thecoupling assembly 11. The plurality of spiral springs 29, which are alsoshown in other drawings, are biased to keep the coupling assembly 11 inthe non-coupled state (cf. FIG. 5). In this way, when the tubing hanger1 has not landed in the spool 101, the coupling elements 17 are in theretracted position within the holes 15 of the carrier ring 13.

FIG. 13 and FIG. 14 illustrate how the coupling elements 17 areretracted to the non-coupled state when the main body 19 moves upwardswith respect to the carrier ring 13. This function is similar to thefunction described in the prior art publication US 6158716 (cf. FIG. 3of the present application). To the main body 19 there is attached aretracting member 37 which extends out from the main body 19. Theretracting member 37 exhibits an inclined retracting surface 37 a whichis adapted to engage a facing inclined surface of the coupling element17 when the main body 19 moves upwards with respect to the carrier ring13. This mutual movement between the main body 19 and the carrier ring13 is provided by the spiral springs 29 functionally arranged betweenthe carrier ring 13 and the main body upper flange 19 a. Hence, whenretrieving the tubing hanger 1 one will not risk that any of thecoupling elements 17 remain in the extended position (coupled position).FIG. 13 shows the coupling element 17 in a coupled position and FIG. 14shows the coupling element 17 in a retracted position. Preferably, oneretracting surface 37 a is arranged on either side of the actuationelement 25.

The coupling assembly 11 of the tubing hanger 1 according to the presentinvention may have one coupling element 17 or more coupling elements 17,for instance 2, 3 or 5, or even more. Furthermore, it may be a tubinghanger 1 adapted for a subsea well. However the tubing hanger 1 may alsobe adapted for an onshore well.

In stead of an axial movement of the actuation portion 27 with respectto the actuation element 25, one may also imagine a tangential directionof the movement. For instance, an actuation ring arranged radiallywithin the actuation elements may be provided with inclined surfaceswhich engage the actuation element when the actuation ring is rotatedabout the centre axis with respect to the carrier ring. The functionalsurfaces (25 a′, 25 b′, 25 c′, 25 d′) of the actuation element 25′ wouldthen be arranged along a horizontal plane, i.e. a plane normal to theaxis of the tubular element (or spool 101).

One can also imagine another actuation element (25) which is made topivot in a radially outward direction in order to exert force andmovement onto the coupling element. The actuation element would then beforced from within at a pivot section and an actuation section, andwould exert force onto the coupling element from a section between thesetwo sections.

1. A tubing hanger adapted to land in a tubular element and comprising acoupling assembly adapted for establishment of a hydraulic couplingbetween the tubing hanger and the tubular element, wherein the couplingassembly comprises: a coupling element adapted to move radially betweenan outer coupled position and an inner non-coupled position, whichcoupling element exhibits an outer surface adapted to establish saidhydraulic coupling with an opposite and inwardly facing surface of thetubular element when forced against it, as the coupling elementcomprises a hydraulic channel adapted to align with a hydraulic channelin the tubular element, and wherein the coupling element comprises aradially inner actuation surface; an actuation element with a contactsurface adapted to exert an actuation force onto the inner actuationsurface in a radially outward direction; wherein the actuation elementexhibits an elongated shape and comprises two actuation sections whichare adapted to be exposed to a radially outward directed force from anactuation arrangement; wherein the contact surface is arranged with adistance from both of said actuation sections; and wherein the actuationelement is adapted to be moved in the radial outward direction in suchway that the movement of at least one of the two actuation sectionsstops after the radial movement of the contact surface stops, whereinthe movement of the contact surface is halted as the coupling elementreaches the coupled position.
 2. Tubing hanger according to claim 1,wherein the actuation element comprises two parallel inclined surfacesadapted to slide simultaneously along two facing inclined surfaces ofthe actuation arrangement.
 3. Tubing hanger according to claim 1,wherein the contact surface of the actuation element or the innersurface of the coupling element exhibits a spherical or convex, curvedshape.
 4. Tubing hanger according to claim 1, wherein in the coupledposition two supporting surfaces of the actuation arrangement areadapted to abut against oppositely arranged and parallel extendingactuation surfaces of the actuation element, of which parallel extendingactuation surfaces one is arranged on each actuation section.
 5. Tubinghanger according to claim 4, wherein the supporting surfaces of theactuation arrangement and the actuation surfaces of the actuationelement are parallel with an axially extending center axis of the tubinghanger.
 6. Tubing hanger according to claim 1 wherein during a firstactuation of the coupling assembly, the actuation element is adapted todeform both in an elastic and plastic manner when the at least one ofthe two actuation sections moves a distance after the movement of thecontact surface has stopped.